The new study focuses on mice, not people. But the researchers say the findings may help explain why smoking is a risk factor for heart disease.

"The best thing to do is quit" smoking, says Daniel Catanzaro, PhD, of Cornell University's Weill Medical College, in a news release.

That's easy to say but often hard to do. If you're one of the many smokers who want to quit smoking, experts say it may take several attempts to kick the habit, but it's worth the effort.

Nicotine Experiment

Catanzaro and colleagues studied five groups of male mice.

One group of mice was exposed to smoke from cigarettes made for research purposes (and which aren't on the market) that deliver 1 milligram of nicotine per cigarette.

Another group of mice was exposed to smoke from Quest 1 cigarettes, which deliver 0.6 milligram of nicotine per cigarette.

A third group of mice was exposed to smoke from Quest 3 cigarettes, which deliver 0.05 milligram of nicotine per cigarette.

A fourth group of mice was exposed to smoke from Eclipse cigarettes, which deliver 0.2 milligram of nicotine per cigarette.

The fifth group of mice wasn't exposed to any cigarette smoke.

Obviously, mice don't smoke cigarettes. So the researchers placed the mice in a cage and piped in cigarette smoke for an hour a day (10-12 cigarettes burned per session) for eight to 12 weeks. The "nonsmoking" mice spent the same amount of time in that cage, but without any smoke exposure.

Nicotine Study's Results

The mice exposed to smoke from cigarettes with higher levels of nicotine developed more plaque buildup in their arteries than the mice exposed to smoke from low-nicotine cigarettes.

But the mice exposed to smoke from low-nicotine cigarettes still had more plaque buildup in their arteries than mice not exposed to tobacco smoke.

Plaque buildup can lead to atherosclerosis, which can lead to heart disease.